exempi: exempi (an implementation of Adobe's XMP)

The Adobe Extensible Metadata Platform (XMP) is a standard for 
processing and storing standardized and proprietary metadata, 
created by Adobe Systems, Inc.

Exempi is an implementation of XMP. It is based on the Adobe XMP SDK
and released under a BSD-style license like Adobe's.

XMP standardizes the definition, creation, and processing of 
extensible metadata. Serialized XMP can be embedded into a 
significant number of popular file formats, without breaking 
their readability by non-XMP-aware applications. Embedding 
metadata ("the truth is in the file") avoids many problems 
that occur when metadata is stored separately. XMP is used 
in PDF, photography and photo editing applications.

The API is C based and means to be used from any language and 
be easier to maintain ABI stability.

The overall changes include:

* STABLE C API/ABI for the library, instead of a C++ template 
  based version.
* GNU friendly build system based on automake.
* Code changes for UN*X systems compatibility.
* Architecture support for 64-bits (x86_64) and others.
* Test suite.
